kbuild: scripts/mkmakefile: dynamic determination of output directory

Rather than fixing the output directory in the generated Makefile,
determine it from the placement of Makefile. This allows moving
the build tree around or accessing it through different mount paths.

(The lastword definition is a compatibility one for make prior to 3.81;
newer make will simply ignore it and use the [faster] built-in.)

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/scripts/mkmakefile b/scripts/mkmakefile
index e0f54b9d8fec..e65d8b33faa4 100644
--- a/scripts/mkmakefile
+++ b/scripts/mkmakefile
@@ -25,8 +25,11 @@ cat << EOF > $2/Makefile
 VERSION = $3
 PATCHLEVEL = $4
 
-KERNELSRC    := $1
-KERNELOUTPUT := $2
+lastword = \$(word \$(words \$(1)),\$(1))
+makedir := \$(dir \$(call lastword,\$(MAKEFILE_LIST)))
+
+MAKEARGS := -C $1
+MAKEARGS += O=\$(if \$(patsubst /%,,\$(makedir)),\$(CURDIR)/)\$(patsubst %/,%,\$(makedir))
 
 MAKEFLAGS += --no-print-directory
 
@@ -35,10 +38,11 @@ MAKEFLAGS += --no-print-directory
 all     := \$(filter-out all Makefile,\$(MAKECMDGOALS))
 
 all:
-        \$(MAKE) -C \$(KERNELSRC) O=\$(KERNELOUTPUT) \$(all)
+        \$(MAKE) \$(MAKEARGS) \$(all)
 
 Makefile:;
 
 \$(all) %/: all
         @:
+
 EOF